SwingUtilities.invokeLater() why is it needed?

Question

Why is it necessary to put GUI update code in SwingUtilities.invokeLater()?

Why cant it be internally taken care of by Swing itself? Why does the caller have to care about how swing handles UI updates?

Answer 1

Swing objects are not thread safe. SwingUtilities.invokeLater() allows a task to be executed at some later point in time, as the name suggests; but more importantly, the task will be executed on the AWT event dispatch thread. When using invokeLater, the task is executed asynchronously; there's also invokeAndWait, which won't return until the task has finished executing.

Some information about the decision not to make Swing thread-safe can be found here: Multithreaded toolkits: A failed dream? [Archived]